The present invention is directed to an apparatus and method for removing oil, hydrocarbons and other organic materials from water, particularly industrial waste waters, ship bilge pump waters, produced water and rainwater collected on offshore oil drilling and production platforms, by adsorption with an oil adsorbent, while electronically monitoring the adsorbent with an embedded probe to determine when the adsorbent needs replacement. More particularly, the present invention is directed to an apparatus and method that includes relatively crude, gravity separation of oil from the water and then contacting the separated water, containing a small amount of hydrocarbons, such as oil and grease, with an organophilic clay to purify the water. During adsorption of the hydrocarbons, the adsorbent is monitored, by the probe, to determine when the absorbent is saturated and should be replaced or regenerated. Further, the present invention is directed towards an improved vessel for housing a plurality of cartridges of the organophilic clay with a removable header for directing filtered water out of the vessel.
Offshore drilling and production platforms used for recovering oil from subterranean formations disposed beneath ocean water includes a number of structural support legs for supporting a plurality of work deck areas at substantial heights above the water level, e.g., disposed from 40 to 100 or more feet above sea level. During the recovery of oil at one or more of these work deck areas, oil, grease and other hydrocarbons are unavoidably spilled onto the deck area(s) and it is not permissible to discard these hydrocarbons into the ocean water. Such work deck areas or platform surfaces are constructed to be fluid-impermeable in order to contain the spilled hydrocarbons on the work deck areas. These hydrocarbons, such as recovered oil, grease, surfactants and other organic contaminants, are directed from the work deck or platform areas, either by water washing or rainwater, into a sump pump container or sump tank where the water and oil separate by gravity so that the water can be removed from a lower portion of the sump tank, for conveyance back to the ocean, and the oil can be pumped from an upper portion of the sump tank into an oil recovery container so that the oil is not returned to the ocean.
These contained deck areas on offshore structures collect a significant amount of water during periods of high rainfall. The rainwater and entrained hydrocarbons, particularly recovered oil, grease and surfactants, are conveyed to the sump tank or collection tank through a gravity drain system from each of the work deck areas. These sump tanks rely on retention time as the primary oil/water separation mechanism in order to skim the lighter density hydrocarbons from a top of the sump tank so that the water can be returned to the ocean.
The sump tanks presently used on offshore platforms suffer from a number of major drawbacks which result in significant amounts of hydrocarbons, particularly oil, paraffins, grease, and refined hydrocarbons being returned to the ocean causing significant ecological contamination. One major drawback of the presently used sump tanks is that they are designed for a maximum of about three inches of rainwater per hour. It has been found that it is not uncommon to experience eight to ten inches of rainfall per hour in areas such as the Gulf of Mexico. Another major drawback of the sump tanks presently used on offshore drilling platforms is that a tank containing a layer of oil disposed above a layer of water will lose the water by evaporation over an extended dry period and the oil layer, as a result, will coat the inside surfaces of the sump tank. This phenomena is known in the art as sheening. As a result of the sump tank sheening, water generated from even a modest rain shower, after this drying period, carries the oil through a water leg or drain portion of the sump tank as the water initially washes lower inner surfaces of the sump tank, thereby carrying the oil to the ocean.
Another water treatment problem associated with offshore oil platforms is the treatment of the aqueous solutions used in acid fracturing processes. Specifically, acidic solutions are commonly pumped down under pressure to cause fractures in the oil producing regions of the formation. As these acidic solutions are returned to the surface, they are often contaminated with oil or hydrocarbons. As discussed above with respect to rainwater, the hydrocarbons must be removed from the solutions before the water is returned to the ocean.
Another problem associated with all auxiliary equipment used on oil platforms is the need for equipment to be designed in a space efficient manner. Specifically, auxiliary equipment, including water treatment equipment, must be designed in as space efficient manner as possible because horizontal square footage on an oil platform is scarce. Therefore, there is a need for water treatment equipment that can treat water at a fast rate, but which is also space efficient.
In accordance with one embodiment of the present invention, an improved apparatus is provided for separating hydrocarbons from a liquid containing water and hydrocarbons. The apparatus includes an improved vessel design. The vessel includes an inlet for conveying contaminated water into the vessel and an outlet for transporting treated water out of the vessel. A removable header is connected to the outlet and housed within the vessel. Permeable conduits are connected to the header and extend upward therefrom. Cartridges containing organophilic media for adsorbing hydrocarbons are then stacked on the permeable conduits. Each cartridge includes a permeable outer cover, a permeable inner tube with the organophilic media disposed therebetween. A pressure drop is provided between the vessel inlet and the vessel outlet, and therefore between the vessel inlet and the permeable conduits. As a result, the contaminated liquid flows radially inwardly through the outer cover of the cartridges, through the media and through the inner tube of the cartridge before flowing into the conduit. Intimate contact between the media and the contaminated liquid results in adsorption of the hydrocarbon contaminents on the media. The header is detachably connected to the treated liquid outlet thereby facilitating removal of the header for replacement or servicing. Accumulated solids, which do not pass through the cartridges, are conveniently collected at the bottom of the vessel and can be flushed out through a drain valve.
In accordance with another aspect of the present invention, an improved method of manufacturing such a vessel is provided. A bottom structure is welded to an open bottom end of a hollow cylinder. The bottom structure includes a drain outlet with a valve disposed exterior to the bottom structure for opening and closing the drain outlet. The bottom structure also includes a treated liquid outlet with an inner end disposed inside the bottom structure. The inside surfaces of the bottom structure and the cylinder are coated with a protective coating to resist corrosion in the presence of salt water and very acidic or basic solutions. A header is connected to the inner end of the liquid outlet and contained within the bottom structure of the vessel. Permeable conduits are then connected to the header and extend upward through the cylindrical section of the vessel. Cartridges, like those described above, are placed singly or are stacked one on top of another with the permeable conduits extending through the inner tubes of the cylindrical cartridges. The improved method enables the weld connecting the bottom structure to the bottom end of the cylinder to be easily coated with the protective coating. Further, because a header is employed, the bottom of the vessel may be used to accumulate solids that do not pass through the cartridges and, because the bottom of the vessel is not needed to collect treated water, a greater portion of the height of the vessel is utilized for cartridges thereby increasing the treatment capacity of each vessel.
In accordance with another embodiment of the present invention, an apparatus and method are provided for treating or polishing an organic compound-containing waste water with a contained volume of organophilic media wherein the organophilic media degrades with time due to continued adsorbance of the organic compound(s) from the waste water onto the media.
In accordance with a preferred embodiment, the preferred media is an organophilic clay and the contained volume of organophilic clay includes a probe disposed within the clay-containing vessel, in contact with the organophilic clay, for monitoring an electrical property of the organophilic clay, preferably by monitoring the electrical conductance or electrical resistance of the organophilic clay and the electrical probe, to obtain a visual or audible signal when it is time to regenerate or replace the organophilic clay (before the organophilic clay has adsorbed so much organic material that its capacity for further adsorbance of organics is insufficient to provide effluent water of sufficient purity). It is anticipated that radio frequency or ultrasonic monitoring of the waste water being treated will serve as suitable substitutes for electrical conductance or resistance measurements.
In accordance with another embodiment of the present invention, the above-described drawbacks of a sump tank system for separation of water from oils and other hydrocarbons have been eliminated by the apparatus and method of the present invention wherein the sump tank water is conveyed for contact with an organophilic media for final separation of hydrocarbons such as oil and paraffins from the water collected on work deck areas of an offshore drilling platform, preferably while the organophilic media is monitored so that it can be replaced before it becomes ineffective.
In brief, one aspect of the present invention is an improved vessel design for accommodating organophilic cartridges in a more space efficient manner. Specifically, the improved vessel design includes an inlet and an outlet. A header is connected to the outlet and disposed inside the vessel near the bottom thereof. The header is connected to one or more permeable conduits that extend upward therefrom. Organophilic media cartridges can then be stacked on the permeable conduits. A pressure drop between the inlet and the outlet causes the contaminated liquid to flow radially inwardly through the permeable outer covers of the cartridges, through the media, through the permeable inner tubes of the cartridges and into the permeable conduits. Because intimate contact between the media and liquid results in adsorption of the hydrocarbon contaminate on the media, treated water passes through the inner tubes of the cartridges and into the permeable conduits. The treated water then flows down through the conduits, through the header and out of the vessel through the outlet.
Another aspect of the present invention is to provide a removable header connected to the treated fluid outlet and disposed inside the vessel. By enabling the header to be removable, the header may be removed and/or replaced when necessary. The employment of a header avoids the use of the bottom of the vessel for collecting treated fluid and thereby enables a greater proportion of the height of the vessel to be used for stacked filter cartridges thereby increasing the capacity of each vessel while not increasing the horizontal footprint of the vessel.
Another aspect of the present invention is directed toward an improved method for manufacturing vessels for accommodating organophilic cartridges for treating hydrocarbon-contaminated water.
Another aspect of the present invention is directed toward a method of manufacturing an apparatus for separating hydrocarbons from a water/hydrocarbon mixture. The manufacturing method includes the steps of providing a hollow cylinder having an open top end, an open bottom end and an inside surface, welding a bottom structure to the bottom end of the cylinder to enclose the bottom end of the cylinder. The bottom structure includes an inside surface with a drain outlet with a valve disposed exterior to the bottom structure for opening and closing the drain outlet. The bottom structure also includes a treated water outlet which has an inner end disposed inside the bottom structure. The method further includes the steps of coating the inside surface of the bottom structure and the inside surface of the cylinder with a protective coating, connecting a header to the inner end of the treated water outlet, connecting at least one permeable conduit to the header, and placing at least one cartridge on the conduit. The cartridge includes a permeable outer cover and a permeable inner tube through which the conduit extends. The cartridge contains an organophilic media between the outer cover and the inner tube. Intimate contact between the media and liquid results in adsorption of the hydrocarbon in the liquid on the media. Finally, the method includes the steps of attaching a removable top structure on the top end of the cylinder.
Yet another aspect of the present invention is directed toward a method of separating water from a liquid that comprises a combination of water and a hydrocarbon contaminate. The separation method includes the step of flowing the liquid into a vessel that includes an outlet, a header connected to the outlet and at least one permeable conduit connected to the header. The conduit passes through a plurality of cylindrical cartridges. Each cartridge includes a permeable outer cover, a permeable inner tube and contains an organophilic media between the outer cover and inner tube. The method further includes the step of providing a negative pressure gradient between a portion of the vessel exterior to the cartridges and the inside of the permeable conduit thereby causing the liquid to flow radially inwardly through the outer cover of each cartridge, through the media and through the inner tube before flowing into the conduit.
Another aspect of the present invention is directed to an apparatus for monitoring adsorbance capacity of an organophilic media by monitoring, continuously or periodically, a property of the liquid being treated by the organophilic media, particularly the electrical conductance or electrical resistance of the liquid being treated. The liquid being treated by the organophilic media for removal of hydrocarbons therefrom can be an industrial waste water, ship bilge pump water, produced water, or, in a preferred embodiment, sump tank water collected on offshore drilling platforms (hereinafter collectively referred to as xe2x80x9cwaste waterxe2x80x9d). The organophilic media preferably is electronically monitored to provide a recognizable audible or visual signal, preferably an alarm, to indicate when the organophilic media should be regenerated or replaced.
Another aspect of the present invention is to provide an improved probe for monitoring the organophilic clay when organophilic clay is used as the organophilic media. A probe in accordance with the preferred embodiment of the present invention is disposed within one of the cartridges and includes two spaced apart elements for monitoring a property of the liquid flowing through the clay. The elements preferably are aligned transversely to the radially inward flow of the liquid through the clay. A convenient property to measure is either the conductivity or resistivity of the fluid by applying a voltage across the two spaced apart elements. An increase in the resistivity or a decrease in the conductivity of the organophilic clay will serve as an indication that the organophilic clay contains hydrocarbon and therefore the organophilic clay needs to be regenerated or replaced. The probe should be placed within the canister and adjacent to the inner tube of the canister as saturation of the organophilic clay will begin from the outside or adjacent to the penneable cover of the canister and proceed inward towards the inner tube.
Another aspect of the present invention is to provide an improved organophilic media canister for separating hydrocarbon contaminate from water that provides an indication as to when the organophilic media has become saturated with hydrocarbon and therefore needs to be replaced or regenerated. The filter canister of the present invention includes an outer cylindrical permeable cover, an inner cylindrical permeable tube, an annular bottom connecting bottom edges of the outer cover to the inner tube, an annular top connecting top edges of the outer cover to the inner tube and, in a preferred embodiment, includes a probe connected between the inner tube and the outer cover, preferably connected to one of the annular top or annular bottom at a middle position. The probe includes two spaced apart elements. The spaced apart elements are each connected to a wire lead. Each wire lead is connected to a control panel. The elements preferably are aligned transversely to a radial flow from the outer cover to the inner tube or, in other words, transversely to a radius defined by a common axis of the outer cover and the inner tube and which extends between the two spaced apart elements. Finally, the filter cartridge includes organophilic media disposed in the space defined by the inner tube, the outer cover, the annular top and the annular bottom. The organophilic media surrounds the probe and comes in intimate contact with liquid flowing through the canister.
Another aspect of the present invention is to provide a method of monitoring the changing adsorbance capacity of a contained volume of organophilic media that is being used to treat an organic compound-containing waste water for removal of organic compounds therefrom such that a visible or audible signal is provided as an indication of when to regenerate or replace the organophilic media.
Another aspect of the present invention is to provide a new and improved method and apparatus for complete separation of oil from water admixed on an offshore oil well drilling platform so that the separated water can be returned to the ocean without ocean contamination, with an oil adsorbent, such as an organophilic media, while monitoring the oil adsorbent for oil saturation.
Another aspect of the present invention is to provide a new and improved method and apparatus for separation of oil and water including a first gravity separation step that provides for separation of water and oil by settling to provide layering of the water in a layer below an oil layer and then draining the lower water layer from the upper oil layer, and thereafter directing at least a portion of the separated water layer through a vessel containing an oil adsorbent for contact with the oil adsorbent for removal (adsorption) of remaining hydrocarbons entrained with the drained water layer, while electronically monitoring the oil adsorbent for oil saturation, such as by installing an electrical conductivity sensor within the oil adsorbent, such that a measurement of electrical conductivity of the oil adsorbent indicates the extent of adsorption capacity remaining in the oil adsorbent.
Another aspect of the present invention is to provide a new and improved method and apparatus for separation of oil and water including a first gravity separation step that provides for separation of water and oil by settling to provide layering of the water in a layer below an oil layer and then draining the lower water layer from the upper oil layer, and thereafter directing the separated water layer through a vessel containing an organophilic media for pressurized contact with the organophilic media, at a pressure of about atmospheric, preferably at least 10 psig above atmospheric, for removal (adsorption) of remaining hydrocarbons entrained with the drained water layer.
The data of Table I show that, at atmospheric pressure and up to less than 10 psig water pressure entering the organophilic media-containing vessel, the effluent is cloudy and contains detectable levels of oil:
The above and other aspects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment read in conjunction with the drawings.